Process for the production of urea

Abstract

A process for producing urea from CO 2 and NH 3 in which the CO 2 and NH 3 are reacted in a reactor, the reaction product containing unreacted carbamate, CO 2 , NH 3 and water is passed into a first decomposer maintained at the same pressure as the reactor, the reaction product is heated and thermally decomposed in said first decomposer to separate a major amount of carbamate from the reaction product, the remaining reaction product is passed into the upper end of a second decomposer maintained at the same pressure as the reactor and first decomposer and said remaining reaction product in said second decomposer is contacted with a stripping stream of inert gas, separating the unreacted compounds from the liquid effluent and a finished product comprising a water solution of substantially pure urea is removed from the lower end of the second decomposer.

We claim: 
     
       1. A process for the production of urea from CO 2  and NH 3  which comprises reacting CO 2  and NH 3  in a reactor to form a liquid reaction product containing unreacted carbamate, CO 2 , NH 3  and water, passing said liquid reaction product containing said unreacted carbamate, CO 2 , NH 3  and water into the upper end of a first stage decomposer maintained at substantially the same pressure as said reactor, in the absence of a stripping agent heating said liquid reaction product and said water in said first stage decomposer and thermally decomposing and separating a major amount of carbamate from said liquid reaction product in said first stage decomposer, passing the liquid effluent remaining after said thermal decomposition and separation in said first stage decomposer from the lower end of said first stage decomposer into the upper end of a second stage decomposer maintained at substantially the same pressure as said reactor and said first stage decomposer and separating the unreacted compounds from said liquid effluent by contacting said liquid effluent in said second stage decomposer with a stripping stream of inert gas and removing from the lower end of said second stage decomposer, as finished product, a water solution of substantially pure urea. 
     
     
       2. A process for the production of urea as recited in claim 1 wherein a mixture of said inert gas and NH 3  are withdrawn from the upper end of said second stage decomposer and said mixture is passed to a condenser where said inert gas is separated from said NH 3  and said NH 3  is passed to said reactor. 
     
     
       3. A process as recited in claim 1 wherein the reactor pressure is not substantially less than 50 and not substantially more than 300 atmospheres. 
     
     
       4. A process as recited in claim 2 wherein the reactor pressure is not substantially less than 50 and not substantially more than 300 atmospheres.